1. Field of the Invention
The present invention relates to a method of manufacturing a flexible piezoelectric energy harvesting device using a piezoelectric composite and a flexible piezoelectric energy harvesting device manufactured by the same, and more particularly, to a method of manufacturing a flexible piezoelectric energy harvesting device using a piezoelectric composite layer produced by mixing piezoelectric powder with polymer, and a flexible piezoelectric energy harvesting device manufactured by the method.
2. Discussion of Related Art
With the rapid development of electronic technologies in the past decade, device miniaturization and power consumption reduction are being accelerated. In order to develop new power capable of replacing typical discardable batteries, studies into a piezoelectric substance capable of converting mechanical energy, such as pressure, force, vibration, etc., into electrical energy are being actively conducted.
As a result, piezoelectric energy harvesting technology has been developed. Piezoelectric energy harvesting technology is expected to be able to be developed as self power source for USN, a portable device, etc. Also, by manufacturing self power source in the form of a flexible thin film device, diversification and expansion of the self power source are expected. Accordingly, requirement for development of a flexible piezoelectric energy harvesting technology is greatly increasing.
A flexible device is manufactured by preparing an organic substrate such as a polymer substrate since the flexible device requires flexibility, and forming an organic thin film as a thin film configuring a functional part on the organic substrate, or transferring an inorganic thin film on the organic substrate. However, a functional part of an organic thin film cannot ensure high performance due to the properties of an organic thin film, and piezoelectric substances are limited. Also, the technology of transferring an inorganic thin film has problems of making a manufacturing process complicated, not maintaining constant yield, and laying limitations on the selection of inorganic substances usable.
Korean Published Patent No. 2011-0072033 (Applicant: Korea Advanced Institute of Science and Technology, Publishing Date: Jun. 29, 2011) has proposed a method of manufacturing a flexible device by separating an upper device from a silicon substrate in such a manner to etch a metal oxide layer that is easily applied on the silicon substrate. In detail, the Korean Published Patent discloses a method of manufacturing a flexible device, including the steps of: forming a first metal layer on a silicon oxide layer on a silicon substrate; forming a device on the first metal layer; annealing the first metal layer to oxidize the first metal to a first metal oxide; etching the first metal oxide to separate the device from the silicon oxide layer; and transferring the separated device to a flexible substrate using a separate transfer layer.
Also, Korean Published Patent No. 2011-0094675 (Applicant: Kee Sam Jeong, Publishing Date: Aug. 24, 2011) discloses PVDF piezoelectric fabric, and a method of manufacturing a micropower energy harvesting system using the PVDF piezoelectric fabric. In detail, the method of manufacturing the micropower energy harvesting system using the PVDF piezoelectric fabric includes the steps of: electrospinning a conductive polymer material onto a substrate to form a lower electrode layer; electrospinning a piezoelectric polymer material on the lower electrode layer to form a piezoelectric layer; and electrospinning a conductive polymer material on the piezoelectric layer to form an upper electrode layer.
Meanwhile, J. H. Jung et. al. “Lead-Free NaNbO3 Nanowires for High Output Piezoelectric Nanogenerator”, ACS Nano, 5, 10041 (2011) has proposed a method of manufacturing a flexible device using a composite produced by mixing NaNbO3 nanowires with polydimethylsiloxane (PDMS). In detail, the method of manufacturing the flexible device includes the steps of: growing an electrode material on a flexible substrate to form an electrode layer; spin-coating a piezoelectric composite produced by mixing NaNbO3 nanowires with PDMS on the electrode layer; performing heat treatment on the piezoelectric composite to harden the piezoelectric composite; attaching the flexible substrate with the electrode layer to the hardened piezoelectric composite to manufacture a flexible piezoelectric energy harvesting device.
A flexible device is manufactured by preparing an organic substrate such as a polymer substrate since the flexible device requires flexibility, and forming a piezoelectric organic thin film on the organic substrate, or transferring an inorganic thin film on the organic substrate. However, a functional part of an organic thin film cannot ensure high performance due to the properties of an organic thin film, and piezoelectric substances are limited. Also, a technology of transferring an inorganic thin film has problems of making a manufacturing process complicated, not maintaining constant yield, and laying limitations on the selection of inorganic substances usable. In addition, in the case of the method of manufacturing the flexible device using the composite produced by mixing NaNbO3 nanowires with PDMS, a manufacturing process of the nanowires is complicated, which makes mass-production difficult.
The present inventors have found that the complexity and limitations of the conventional methods can be overcome when a flexible piezoelectric energy harvesting device is manufactured using a piezoelectric composite layer produced by mixing piezoelectric powder with polymer, so that a highly efficient flexible piezoelectric energy harvesting device having various sizes and patterns can be manufactured through a simple process.